There is a known ink-jet recording head which uses an electro-mechanical conversion element, such as a piezoelectric element, as the pressure converting means for variably applying pressure on the ink within the ink chamber. A resiliently deformable vibration plate, which forms a wall of the ink chamber, is deformed by a driving means, by use of the pressure converting means, so as to eject an ink drop by varying the volume and/or pressure within the ink chamber. The so-called piezoelectric type ink-jet recording head corresponds to such an ink-jet recording head. For example, Japanese Laid-Open Patent Application No. 8-108534 proposes such a piezoelectric type ink-jet recording head.
A description will be given of the piezoelectric type ink-jet recording head, by referring to FIGS. 1 and 2. FIG. 1 is a cross sectional view showing the piezoelectric type ink-jet recording head cut along a longitudinal direction of a pressure-applied ink chamber, that is, along a direction perpendicular to a direction in which nozzles are arranged. FIG. 2 is a cross sectional view showing the piezoelectric type ink-jet recording head cut along a direction perpendicular to the longitudinal direction of the pressure-applied ink chamber, that is along the direction in which the nozzles are arranged.
The ink-jet recording head shown in FIGS. 1 and 2 includes an ink chamber substrate 211 and a nozzle plate 218 which are connected. A pressure-applied ink chamber 214 communicates to a nozzle 213 which ejects the ink drop. A common ink chamber 219 supplies the ink to the pressure-applied ink chamber 214 via a connecting part 220. A piezoelectric element 217 is provided on a base substrate 212, on the outer side of a vibration plate 216 which forms a portion of a wall of the pressure-applied ink chamber 214.
The vibration plate 216 undergoes resilient deformation as the piezoelectric element 217 is deformed. In order to efficiently convert a displacement of the piezoelectric element into a volume change of the pressure-applied ink chamber 214, the rigidity of the vibration plate 216 is normally smaller than that of other surfaces forming the pressure-applied ink chamber 214. In other words, the compliance of the vibration plate 216 is normally larger than that of the other surfaces forming pressure-applied ink chamber 214. In addition, the common ink chamber 219 is connected to an ink tank (not shown), and a support member 221 is provided between the ink chamber substrate 211 and the base substrate 212.
The piezoelectric element 217 is deformed by applying a voltage to the piezoelectric element 217 from a driving circuit (not shown), to displace the vibration plate 216 so as to increase or decrease the volume of the pressure-applied ink chamber 214. When the volume of the pressure-applied ink chamber 214 increases, the internal pressure of the pressure-applied ink chamber 214 decreases, and the ink from the common ink chamber 219 is supplied to the pressure-applied ink chamber 214 via the connecting part 220.
Thereafter, the piezoelectric element 217 is driven so as to increase the internal pressure of the pressure-applied ink chamber 214. In other words, when the piezoelectric element 217 is driven so as to decrease the volume of the pressure-applied ink chamber 214, the internal pressure of the pressure-applied ink chamber 214 increases, and the ink is ejected from the nozzle 213 in the form of an ink drop 222. The ink drop 222 adheres on a recording medium (not shown) such as paper, to record an image or the like on the recording medium.
The ink-jet recording head may use elements other than the piezoelectric element for the pressure converting means for causing the ink to be ejected, such as a thermal actuator, a shape memory alloy actuator and an electrostatic actuator. The thermal actuator utilizes a phase change caused by film boiling of the ink by using an element which converts electricity into heat, such as a heating resistor. The shape memory alloy actuator uses a metal phase change caused by temperature change. The electrostatic actuator uses electrostatic force.
When ejecting the ink drop from the ink-jet recording head as described above, it is necessary to increase the pressure of the pressure-applied ink chamber. In addition, the generated pressure not only causes the ink to be ejected, but is also applied to the common ink chamber. However, when the pressure applied to the common ink chamber is again applied to the pressure-applied ink chamber, the pressure of the pressure-applied ink chamber varies.
Particular in the case of the ink-jet recording head having a large number of nozzles, the pressure change at the time of a multi-channel drive is large, and causes resonance (mutual interference) of the ink chamber. If the resonance frequency of the vibration matches the driving frequency of the recording, the ink ejection is affected thereby to deteriorate the picture quality of the recorded image.
In order to prevent the problem associated with the resonance frequency, it is necessary to increase the pressure damping efficiency of the common ink chamber. Generally, this is achieved by setting the volume of the common ink chamber to a relatively large value. On the other hand, a Japanese Laid-Open Patent Application No. 6-191030 proposes another method which provides a plurality of damper chambers between the ink chamber and the common ink chamber, so as to absorb a pressure change within the ink chamber.
In addition, although for a different purpose, a Japanese Laid-Open Patent Application No. 2000-158668 proposes a method of providing a plurality of damper chambers within an ink supply passage from the ink tank to the ink-jet recording head, in order to absorb a change in the ink supply pressure. In other words, the damper chambers are provided to reduce the pressure change when supplying the ink from the outside to the common ink chamber of the ink-jet recording head.
However, since the damper chamber is provided for each individual ink chamber of the ink-jet recording head according to the Japanese Laid-Open Patent Application No. 6-191030, it is difficult to sufficiently reduce the rigidity of the damper chamber, and it is difficult to effectively absorb the pressure. Furthermore, the structure of the ink-jet recording head becomes complex, thereby requiring a complex production process to produce the ink-jet recording head. Recently, the trend is for the number of nozzles of the ink-jet recording head to increase in order to cope with the demands for high-speed recording, but the structure proposed in the Japanese Laid-Open Patent Application No. 6-191030 is unsuited for application to this trend.
On the other hand, the ink-jet recording head proposed in the Japanese Laid-Open Patent Application No. 2000-158668 reduces the pulsation in the ink supply, and does not absorb the pressure change of the common ink chamber when the ink-jet recording head is driven. In addition, the structure of the ink-jet recording head becomes complex, thereby requiring a complex production process to produce the ink-jet recording head.